A 14-year-old boy lay "quivering" in a pool of blood after being stabbed at least nine times by a rival gang, a court has heard.
Jaden Moodie was attacked by three men in Leyton, north-east London, on 8 January, the Old Bailey has been told.
In a witness statement, read out in court, one man said he saw three men "stomping on someone" on Bickley Road.
Ayoub Majdouline, 19, of Wembley in north London, denies murder and possession of a knife.
The witness said he had been sitting at home when he heard a loud crash on Bickley Road.
He saw three people get out of a Mercedes before one of them began "stomping on someone" on the ground, the court heard.
He also saw someone with a "London rudeboy accent, kicking someone on the ground" before someone said, "quick, let's get out of here".
The trial of Mr Majdouline has previously heard Jaden had been riding his moped around the streets where the "Beaumont Crew" gang was known to operate, and with whom he was linked.
"He dealt drugs for them and is likely to have been doing just that on this particular evening - he must have felt safe in this area and it is unlikely that he anticipated that anything untoward might happen to him," prosecutor Oliver Glasgow QC said.
Mr Majdouline, who is allegedly linked to rival gang the "Mali Boys", had been in a stolen Mercedes which was driven at Jaden, causing him to be "catapulted" over the bonnet, Mr Glasgow added.
The defendant and two others, all armed with knives, then got out of the car and began stabbing Jaden repeatedly, jurors heard.
The attack "violent and frenzied" attack lasted 14 seconds, the court has been told.
Another witness told the court Jaden was "quivering" and that "thick trails of blood" were coming from the car the teenager lay underneath.
Forensic practitioner Ian Hounsell, who was in the area at the time of the attack, told jurors he could hear the teenager "grunting" and that he noticed several slit marks at the back of Jaden's jacket.
He administered CPR, but the 14-year-old was pronounced dead at 19:09 GMT.
Post-mortem examinations detected Jaden had previously used cannabis, the court was told.
The trial continues.